1. Field of the Invention
The invention relates to a forceps for an endoscopic operation which is passed through a trocar to be used for performing an endoscopic operation in the body cavity.
2. Description of the Related Art
Recently, in various kinds of operations such as cholecystectomy, an endoscopic operation is widely performed. Such an endoscopic operation is performed without making a large incision and with thrusting plural trocar sheaths (hereinafter, referred to merely as "trocars") which are thin tubular members, into the somatic layer, and passing a surgical instrument and an endoscope through the trocars.
In an endoscopic operation, forceps such as a grasping forceps which grasps organs, and a cutting forceps which cuts organs are necessary. Generally, such forceps are configured so that a pair of members in each of which a grip piece on the side of the basal end and a forceps piece on the side of the tip end are integrally formed are rotatably coupled to each other at a fulcrum in an X-shape.
A forceps is passed through a trocar under a state where forceps pieces at the tip end are closed so as to reduce the size in section. In the body cavity, preferably, the tip end forceps pieces are widely opened.
As shown in FIG. 9, however, the open angle .theta. of tip end forceps pieces 91 is restricted by the inner diameter of a trocar 100. In a related art forceps for an endoscopic operation which is configured as described above, therefore, the open angle .theta. is restricted by the both end openings of the trocar 100.
The open angle .theta. is maximum when the fulcrum 92 is at to the middle of the trocar 100 in the longitudinal direction as shown in FIG. 9, and hence Tan(.theta./2) cannot be made large. Unless the trocar 100 is made unrealistically thick and short, consequently, a large open angle .theta. cannot be attained.
Even when a diseased part is slightly large, therefore, the part cannot be surely grasped or cut. As a result, an endoscopic operation cannot be adequately performed.